NTSB Factual Report

On June 29, 2015, about 1130 central daylight time, an experimental, amateur-built Guice Zodiac 601XL airplane, N253DG, was substantially damaged during a forced landing near Seagoville, Texas. The pilot and passenger were not injured. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The flight originated from the Lone Star Executive Airport (CXO), Houston, Texas, about 1000. The intended destination was the Mesquite Metro Airport (HQZ), Mesquite, Texas.

The pilot reported that the high oil temperature warning illuminated as he approached the destination airport. His attempts to remedy the situation were successful, but only for a few minutes. The high oil temperature warning illuminated again and the engine subsequently began running rough. He insured that the fullest fuel tank was selected and turned on the fuel boost pump. However, smooth engine operation could only be obtained by reducing the engine speed to about 2,000 rpm. Unfortunately, at that power setting, the airplane would not maintain altitude. With a dense wooded area between the current position and the airport, the pilot setup for a forced landing to an open hay field. However, a set of power lines intervened and he ultimately selected a field with waist high grass. During the landing, the nose landing gear collapsed and the airplane nosed over resulting in fuselage and wing damage.

Federal Aviation Administration inspectors conducted a postaccident examination. The examination did not reveal any mechanical failures with respect to the engine assembly. The pilot reportedly informed the inspectors that he intentionally ran the engine with about one-half quart more oil than specified in an attempt to reduce engine operating temperatures. When checked at the accident site, the engine oil quantity was higher than the upper limit on the oil dipstick.

The Jabiru 3300 is a six-cylinder, horizontally opposed, air cooled, direct drive, reciprocating engine. It is capable of developing 120 horsepower at 3,300 rpm. The accident engine, serial number 33A1561, had accumulated about 195 hours total time in service. The most recent condition inspection was completed on September 17, 2014, at 163.6 hours total time in service. The logbook provided did not contain any entries subsequent to the condition inspection.

Jabiru issued a service bulletin regarding engine cooling applicable to the Jabiru J230 light sport airplanes, which are powered by the Jabiru 3300 engine. The service bulletin specifically noted that the engine oil level has a "strong effect on oil temperatures." In addition, the bulletin stated: "For all 3300 engines, the lowest oil temperatures are achieved when the oil level is set on the lower dipstick mark. . . . Note that testing has shown that setting the oil level slightly above the upper dipstick mark (i.e. slightly over-full) can result in oil temperatures 15 [degrees] C higher than when set at the lower mark."

NTSB Probable Cause

The engine overheating, which resulted in a partial loss of engine power, due to the pilot's operation of the engine with a higher-than-specified oil quantity level.